1. Field of the Invention
The present invention relates to a module structure of a communication device performing input and output of electric signals or optical signals and, more particularly, to an engagement structure between a module and a cage for accommodating the module.
2. Description of the Related Art
There is known a module structure in which a communication device performing input and output of electric signals or optical signals is modularized and the module can be inserted into and detached from a cage accommodating the module.
As a modularized communication device, there are, for example, an E/O module, which changes an electric signal into an optical signal to send it, and an O/E module, which changes an optical signal into an electrical signal to receive it.
In the field of an optical-communication equipment, which is oriented to minimization, standardization (multi-source) of the specification of structural elements has been progressed, and the standard (MSA: Multi Source Agreement) is defined with respect to a size of the module and the cage, a compatibility of a light/electricity interface part, a mechanical compatibility regarding mounting and demounting a module to a cage, etc.
As an insertion/detachment mechanism of a module to a cage, there is known a structure which disengages the module from the cage by causing the handle of the module to rotate from an accommodated position to a withdrawal position (for example, refer to Japanese Laid-Open Patent Application No. 2005-249892).
FIGS. 1A, 1B and 1C are perspective views showing an insertion/detachment mechanism of a conventional modularized optical communication apparatus.
FIG. 1A shows a state where a module 1 is accommodated in a cage 4, FIG. 1B shows a state where the module 1 is disengaged from the cage 4 by rotating a handle 3 of the module 1 from an accommodated position to a withdrawal position, and FIG. 1C shows a state where the module 1 is pulled out of the cage 4 by pulling the handle 3.
In FIG. 1A, the handle 3 is rotated in a direction of an arrow 50 by being supported by a connector fitting part 121 so as to be in an upstanding state. This position of the handle 3 is referred to as an accommodated position. In this state, an engagement pin 122 provided in a T-shaped tongue piece 21 of the module 1 protrudes from an engagement aperture 43 provided in an I-shaped tongue piece 42 of the cage 4, and, thereby, the module 1 is in engagement with the cage 4 and is in a restrained state.
As shown in FIG. 1B, when the handle 3 of the module 1 is rotated in a direction of an arrow 51, a plate cam 31 formed on an end of a rotation shaft 32 of the handle 3 rotates in a direction of an arrow 56 and the T-shaped tongue piece 21 is pressed down in a direction of an arrow 52. As a result of the I-shaped tongue piece 42 of the cage 4 being bent downward by following the movement, the engagement between the engagement pin 122 and the engagement aperture 43 is cancelled, and, thereby, the module 1 is released from restraint and falls into a withdrawal/detachable state.
In FIG. 1C, the T-shaped tongue piece 21 is maintained to be pressed down by drawing the module 1 in a direction of an arrow 53 by pulling the handle 3. On the other hand, the I-shaped tongue piece 42 returns in a direction of an arrow 54 by a resilient force after it is separated from the T-shaped tongue piece 21.
In the Multi Source Agreement (MSA) regarding modules, there is a specification with respect of a height direction of a module, which gives a limitation to a length of a handle provided to a module.
In FIG. 1B, since the handle 3 needs to rotate without interference with the connector fitting part 121, there is a limitation in shifting the rotation shaft 32 of the handle 3 to the engagement pin 122. A length of the T-shaped tongue piece 21, which links a cam action according to a rotation of the handle 3 to a disengagement action of the engagement pin 122 and the engagement aperture 43, must be longer than a predetermined value.
Since the length of the T-shaped tongue piece 22 cannot be shortened due to a limit according to the agreement of module (MSA), if the T-shaped tongue piece 22 is displaced minutely, the engagement state by the engagement pin 122 and the engagement aperture 43 becomes unstable.
Especially, in FIG. 1A, in a state where the handle 3 is at the accommodated position, since the engagement by the engagement pin 122 and the engagement aperture 43 is maintained mainly by the resilient force of the I-shaped tongue piece 42, if the T-shaped tongue piece 22 is displaced due to aged deterioration, the engagement state by the engagement pin 122 and the engagement aperture 43 becomes unstable.